Long a favorite punching bag for frustrated builders, San Francisco's Planning Department finds itself a darling of an unlikely crowd: modern architects.

A two-year push by Mayor Gavin New≠som and planning director Dean Macris to heighten design quality and encourage modern architecture has transformed the city's approach to planning, architects say. The changes have occurred on scales both mind-blowing and modest.

On the extravagant end are projects such as the Transbay Terminal and Tower, most likely to be designed by Cesar Pelli, and Renzo Piano's proposed "bamboo shoots" -- a pair of 1,200-foot towers at Mission and First streets.

Elsewhere, designs by Enrique Norton for the Mexican Museum at 706 Mission St. and Beacon Capital Partners' new HOK-designed office building recently approved for 535 Mission St. are generating buzz.

But far from the sexy marquee downtown buildings, experimental design is also taking root in neighborhoods such as Potrero Hill, Bernal Heights and the Mission District, according to senior planner Craig Nikitas, who heads the city's better design initiative.

"This initiative that Dean started has been really well-received by the development community -- they have really responded to the challenge we have raised," Nikitas said.

In his new role as design gatekeeper, Nikitas delves into the nitty-gritty of the biggest proposals that come through the door -- and the smallest. Although insisting that buildings maintain the scale that make the city's neighborhoods famously distinctive and walkable, he pushes sustainable design and, when appropriate, interesting shapes and materials such as metal, glass or poured cement.

Some of the directives have been modest. The department has made it a policy not to allow stucco-covered foam trim, for example, which "lacks the crispness of wood" and tends to crack and darken over time. Faux-

Victorians with bay windows and stucco-clad Mediterraneans are not always the best solutions, he said.

"You can deviate from materials but still respect scale," Nikitas said. "Dean has enabled me to spend hours every day with neighborhood planners reviewing designs for additions and new single-family homes and really think about massing and the pedestrian realm."

An international trend

Part of the change is global: The push toward celebrity architects, which started with Frank Gehry's Guggenheim museum in Bilbao, Spain, has spread everywhere. Handel Architects principal Glenn Rescalvo said San Francisco's interest in attracting top international designers "is a way for the city to gesture that they want better architecture."

"It's made a lot of developers a bit nervous, but it's encouraged them to go out and get better architects or rethink their strategy," said Rescalvo, whose office designed the Millennium Tower under construction at 301 Mission St.

"These are good small projects in tough neighborhoods that get done," Rescalvo said. "The Planning Department has been behind these projects regardless of some negative neighborhood input."

Charles Dilworth, a principal with Studios Architecture, said a receptiveness to modernism has been growing for the past five to eight years, but it has accelerated since Newsom and Macris made it an explicit policy about two years ago.

"There is a greater trend toward better design in general, and modern architecture has a much greater public appeal than it did five to 10 years ago," Dilworth said. "But it still takes courage to step out and say, 'I want this.' "

'Barrier to entry'

While San Francisco-based Studios Architects designed the Foundry Square buildings in the South of Market area, it has focused on university campuses and corporate headquarters around the world. Dilworth said San Francisco's highly democratic process has tended to filter out "anything the least bit experimental" and led to watered-down buildings.

"It was somewhat of a barrier to entry," Dilworth said. "It's nice to do big buildings in the city, but it's not so nice if everybody in creation has a say in what it looks like and how it works. It doesn't produce the best results, as we have seen."

While it might have led to some mediocre office towers, the city's heavy public process has helped preserve its walkable, low-scale and distinct neighborhoods.

"Most San Franciscans are pretty conservative about their own neighborhood," Dilworth said. "It's hard to get anything built in residential neighborhoods, and there is something to be said for that. The controls are there to keep the monstrosities out -- but a lot of good things are kept out as a result."

Steely, who designed the acclaimed home at 306 Mullen St. in Potrero Hill, said city planners are more willing to go to bat for projects that have neighborhood opposition if the design is seen as thoughtful and contextual.

At the same time, architects are responding to a new level of sophistication among clients; magazines such as Dwell have made modernist architecture mainstream. Steely compared Mario Botta's "conservative" 1995 San Francisco Museum of Modern Art with the two newest museums: Herzog & deMeuron's deYoung Museum and Renzo Piano's California Academy of Sciences, which is under construction in Golden Gate Park.

"They are not even on the same planet," Steely said. "Ten years ago, it was a big deal to see any modern house in San Francisco. Now there is so much modernism you can start to be critical of it."

In addition, much of the modernism is being driven by the fact that the city's few remaining empty lots tend to be odd-shaped or on steep terrain.

"They have been protected by being difficult," he said. "A developer couldn't just buy it and slap something stupid there."

The best yet to come

Mark Hornberger, a principal with Hornberger + Worstell, said the new appreciation for high-quality modernism has extended to the renovations of historic buildings. Hornberger's firm is working on converting Ghirardelli Square into fractional ownership residences and is designing the revamped 140 New Montgomery St. for Wilson Meany Sullivan. Both will combine meticulous restoration with modern interiors. Hornberger said the reception for these buildings, "has been very different than it would have been 15 to 20 years ago."

"Cities become living museums if you don't allow them to change," Hornberger said. "We're trying to save these wonderful landmarks by increasing utility and revenue stream. The idea is that contemporary design can enhance historic structures rather than detract."

The best might be yet to come, Nikitas said. Many of the projects being entitled now won't be built until 2009 or 2010. Nikitas is excited about 535 Mission St., a tapered tower he said "totally integrates green building design with modernity."

"It's an intellectually rigorous building form -- I'm not sure that design would have been approved a decade ago," he said.

And he is also looking forward to several new Saitowitz buildings in the planning stage.

"He is almost like a glass sculptor," Nikitas said. "His buildings are about glass and concrete and light. ...Where they are appropriate, they are magical."